Figure 15: Melting relations among minerals in the system SiO2 (quartz)–KAlSiO4 (kalsilite)–Mg2SiO4 (forsterite). Temperatures next to compositions refer to the melting points of those compositions in °C. Protoenstatite, instead of enstatite, is produced in experiments of this type. The compositions of protoenstatite and enstatite are identical, but their structures differ.